The prior art comprises cogged belts manufactured in thermoplastic material in which reinforcing metal cores are sunk, arranged in a longitudinal direction and constituted by a plurality of cords or flanked filaments; the belts have high resistance to traction and are thus suitable for power transmission and synchronised transport of articles; in their disfavour, they are expensive and rigid.
Where transport of articles does not require high power mechanisms, for example in some applications in the food industry, homogeneous belts are used (for example made entirely of a thermoplastic material) which are flat, i.e. they have a constant thickness along the transversal development thereof, and on which one or more longitudinal centring guides can be additionally applied, either continuous or cogged; the centring guides are destined to engage in corresponding annular gullies (respectively hollow or cogged) afforded in the driven and drive pulleys on which the belt is destined to wind. These belts exhibit a greater flexibility inasmuch as they are not provided with reinforcement cores, so that they can wind on pulleys of smaller diameter, but their low mechanical resistance limits their range of application.
Italian patent no. 1,170,292 describes a process and a device for manufacturing a reinforced cogged belt, i.e. with metal reinforcing cores.
The device comprises: a rotating support wheel activated in rotation by actuator organs, on a periphery of which an annular gully is afforded; a containment cover (for example a ring-wound belt) which faces a circular sector of the rotatable wheel to form a hollow chamber exhibiting an inlet section with respect to a rotation direction of the wheel; a ring-shaped member provided with an external cogging, which member winds about the rotatable wheel and about a driven wheel engaging with the relative base in the annular gullies of both the wheels (drive and driven); and an extrusion nozzle arranged at the inlet section of the hollow chamber, destined to inject molten plastic material on the cogged shape.
A metal reinforcing cord is previously spiral-wound on the ring-shaped cogging, ends of which cord are fixed to the cogging itself.
The molten plastic material on the cogging and retained by the walls of the gully of the rotating support wheel and by covering solidifies during transit along the hollow chamber; thus a length of reinforced cogged belt is formed, a head end of which is subsequently joined to the tail end thereof at the inlet section of the hollow chamber by release of a molten thermoplastic material from the extrusion nozzle, thus obtaining a ring-wound belt.
With suitable adaptation, continuous reinforced cogged belts can be obtained; alternatively, by removing the use of a reinforcing cord, it is possible to obtain cogged ring-wound belts or continuous cogged ring-wound belts made entirely of a thermoplastic material.